FSharp.Control.TaskSeq/src/FSharp.Control.TaskSeq.Test/TaskSeq.Empty.Tests.fs at 32c57b37f8e11fa0b1947b098ff64680ac915d9d · fsprojects/FSharp.Control.TaskSeq · GitHub

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module TaskSeq.Tests.Empty

open System.Threading.Tasks
open Xunit
open FsUnit.Xunit

open FSharp.Control


[<Fact>]
let ``TaskSeq-empty returns an empty sequence`` () = task {
    let! sq = TaskSeq.empty<string> |> TaskSeq.toListAsync
    Seq.isEmpty sq |> should be True
    Seq.length sq |> should equal 0
}

[<Fact>]
let ``TaskSeq-empty returns an empty sequence - variant`` () = task {
    let! isEmpty = TaskSeq.empty<string> |> TaskSeq.isEmpty
    isEmpty |> should be True
}

[<Fact>]
let ``TaskSeq-empty in a taskSeq context`` () = task {
    let! sq =
        taskSeq { yield! TaskSeq.empty<string> }
        |> TaskSeq.toArrayAsync

    Array.isEmpty sq |> should be True
}

[<Fact>]
let ``TaskSeq-empty of unit in a taskSeq context`` () = task {
    let! sq =
        taskSeq { yield! TaskSeq.empty<unit> }
        |> TaskSeq.toArrayAsync

    Array.isEmpty sq |> should be True
}

[<Fact>]
let ``TaskSeq-empty of more complex type in a taskSeq context`` () = task {
    let! sq =
        taskSeq { yield! TaskSeq.empty<Result<Task<string>, int>> } // not a TaskResult, but a ResultTask lol
        |> TaskSeq.toArrayAsync

    Array.isEmpty sq |> should be True
}

[<Fact>]
let ``TaskSeq-empty multiple times in a taskSeq context`` () = task {
    let! sq =
        taskSeq {
            yield! TaskSeq.empty<string>
            yield! TaskSeq.empty<string>
            yield! TaskSeq.empty<string>
            yield! TaskSeq.empty<string>
            yield! TaskSeq.empty<string>
        }
        |> TaskSeq.toArrayAsync

    Array.isEmpty sq |> should be True
}

[<Fact>]
let ``TaskSeq-empty multiple times with side effects`` () = task {
    let mutable x = 0

    let sq = taskSeq {
        yield! TaskSeq.empty<string>
        yield! TaskSeq.empty<string>
        x <- x + 1
        yield! TaskSeq.empty<string>
        x <- x + 1
        yield! TaskSeq.empty<string>
        x <- x + 1
        yield! TaskSeq.empty<string>
        x <- x + 1
        x <- x + 1
    }

    // executing side effects once
    (TaskSeq.toArray >> Array.isEmpty) sq |> should be True
    x |> should equal 5

    // twice
    (TaskSeq.toArray >> Array.isEmpty) sq |> should be True
    x |> should equal 10
}